The present invention relates to an automatic air conditioner charging station for charging refrigerant and oil into air conditioner systems, particularly automotive air conditioner systems.
There have been provided systems for automatically charging, in the proper sequence, and in appropriate amounts, oil and refrigerant to automotive air conditioner systems. In Proctor, et al. U.S. Pat. No. 4,513,578, there is disclosed an air conditioner charging station having a weighing scale on which are mounted reservoirs for oil and refrigerant. An electronic sequencing unit in the form of a computer module senses the weight loss of the reservoirs as first the oil is charged into the air conditioner and then refrigerant is charged into the air conditioner. The apparatus disclosed in this patent has provision for entering into the computer the required amount of oil and refrigerant for the particular air conditioner unit being serviced, and then charges the oil and refrigerant sequentially and in the amounts commanded or entered into the memory of the computer.
Wagner, U.S. Pat. No. 3,785,163 discloses apparatus for charging an air conditioner system including a conduit having one end connected to a valve to which is connected a refrigerant container, the other end of the conduit connected to a manifold, the manifold providing a pair of discharge passages, one for connection to the high pressure side of the compressor and the other to the low pressure side of the compressor, with individual control valves for each of the passages.
White, U.S. Pat. No. 3,873,289 provides an air conditioner charging system with connections to the high pressure side and low pressure side of a compressor, with refrigerant and oil being charged to the low pressure side of the compressor. In addition, a dump line is provided, connected to the high pressure side of the compressor.
Koser, U.S. Pat. No. 4,285,206 provides an automatic refrigerant charging system which includes a micro-processor and a key board for inputting data, and further provides for evacuation from both the high and low pressure sides of the compressor as well as for the charging to both the high and low pressure sides of the compressor.
Cain, U.S. Pat. No. 4,261,178 is a further disclosure of a system for evacuating from both the high and low pressure sides of a compressor.
Lower, et al., U.S. Pat. No. 4,364,236 provides a high pressure switch which is employed as a safety device for terminating the operation of a metering pump delivering refrigerant to the compressor in the event that a valve is closed on the outlet side of the pump, which valve should have been opened. This patent also discloses the utilization of a heater and heat control for a refrigerant container.
Bruce, U.S. Pat. No. 3,695,055 provides an air conditioner charging system in which there is provision for sensing the temperature of the refrigerant being pumped, the sensed temperature, if too low, causing a shut off of the feeding of refrigerant.
Saunders, U.S. Pat. No. 4,245,480 utilizes, in a refrigerant charging system, signals representative of indoor and outdoor temperature, which are supplied to a super heat reference circuit which generates a desired super heat signal.
A number of problems have arisen in the operation of automatic air conditioner charging stations. For example, where a manual dump valve have been provided, it is sometimes permitted to remain open by the operator during the charging cycle, resulting in an insufficient quantity of refrigerant reaching the compressor. Further, in some of these units, the speed of evacuation and the speed of charging have been unacceptably slow.
When a partial or supplementary charge is being delivered, the mechanic may find it necessary to start the automobile engine to create a lower pressure on the low pressure side of the compressor in an attempt to draw more refrigerant from the refrigerant supply container. In this situation, there will occur refrigerant circulation from the high pressure side to the low pressure side of the compressor through the interconnection, or cross-over, without delivery of refrigerant from the refrigerant supply container into the air conditioner.
Another problem which has been noted is that upon discharging of an air conditioner where the pressure in the high side of the system is excessively high, for example is 120 psig or above, there results an excessively fast discharge of fluid, there being discharged not only refrigerant, but also oil from the air conditioner. When the oil is discharged, the system foams since the dissolved refrigerant boils off. This is highly undesirable.